After downloading the latest quicktime update, my imac g5 (w/ OS X) has gone sideways on me. I dont have the technical language to describe the phenomenon but will try to describe what happens. The desktop refreshes every 30 seconds or so and deadens the window (e.g. word doc or internet page) open on the desktop. I then have to click on that window to resume use of it. What is happening? Is this a virus? What do I need to do to repair my imac? Assistance, please.